Introduction of Bt cotton hybrids in India: Did it change the agronomy?

The introduction and subsequent rapid adoption of Bt. transgenic cotton hybrids (Gossypium species) have undoubtedly been the most significant event in the history of cotton in India. Besides providing resistance against lepidopteron pests, the Bt. hybrids matured earlier, were more determinate, had a rapid leaf area development, retained more early set fruiting forms and perhaps have a shallower root system. Both researchers and farmers during the last decade have been fine-tuning the agronomy to maximize the benefits from Bt cotton. Some prominent changes accompanying this technology have been, compulsory seed treatment with imidachloprid, advancement in sowing wherever supplemental irrigation was available, a delay in sowing in the traditional rainfed till the soil profile absorbs sufficient moisture, application of atleast 25% higher fertilizer dose, shift towards balanced fertilization, foliar application of K and micronutrient mixtures. Adoption of drip irrigation and fertigation, more widespread use of booth pre-emergence (pendimethalin) and post-emergence herbicides (quizalofop ethyl and pyrithiobac sodium), practice of stale seed bed technique for weed management, pruning and extension of crop duration are some other agro techniques which are being adopted by Bt cotton farmers.